Air conditioning systems are currently commonplace in homes, office buildings and a variety of vehicles including, for example, automobiles. Over time, the refrigerant included in these systems becomes depleted and/or contaminated. As such, in order to maintain the overall efficiency and efficacy of an air conditioning system, the refrigerant included therein may be periodically replaced or recharged.
Portable carts, also known as recover, recycle, recharge (“RRR”) refrigerant service carts or air conditioning service (“ACS”) units, are used in connection with servicing refrigeration circuits, such as the air conditioning unit of a vehicle. The portable machines include hoses coupled to the refrigeration circuit to be serviced. A vacuum pump and compressor operate to recover refrigerant from the vehicle's air conditioning unit, flush the refrigerant, and subsequently recharge the system from a supply of either recovered refrigerant and/or new refrigerant from a refrigerant tank.
Refrigerant vapor entering the ACS unit first passes through a system oil separator or accumulator to remove oil entrained in the refrigerant from the air conditioning system. Next, the refrigerant passes through a filter and dryer unit to remove contaminants and moisture from the recovered refrigerant and the refrigerant is then pressurized by a compressor.
Refrigerant vapor is very hot as it exits the compressor during an AC recovery cycle. In a typical flow path, this hot refrigerant enters a compressor oil separator, which separates any compressor oil entrained in the refrigerant from the compressor pass-through from the refrigerant vapor. The compressor oil is returned to the compressor, while the refrigerant vapor continues along the flow path into a heat exchanger located within the system oil separator or accumulator found earlier in the path. In some refrigerant systems, the compressor oil separator is located within the system oil separator to function as the heat exchanger for the system. The refrigerant is then typically stored in a refrigerant storage tank, also referred to herein as an internal storage vessel (“ISV”).
As refrigerant enters the system oil separator, heat from the heat exchanger boils the refrigerant to a vapor, while the oil entrained in the vapor remains in liquid form, separating from the vaporized refrigerant. The refrigerant vapor continues through the recovery process, while the oil settles to the bottom of the system oil separator and is collected for disposal or reuse.
However, when a recovery operation is first initiated in a current ACS unit, all components in the ACS unit are typically at ambient temperature. Therefore, when the recovery operation is first initiated, the heat exchanger is at essentially the same temperature as the refrigerant entering the system oil separator. As a result, no heat is transferred to the refrigerant, and the refrigerant does not vaporize. If the heat exchanger does not reach an adequate temperature to vaporize the refrigerant, the oil is not separated from the refrigerant and remains in the refrigerant. Additionally, a large portion of the oil in the air conditioning system travels at the beginning of the recovery operation, when the velocity of the refrigerant entering the ACS unit is high. As a result, a significant amount of system oil can be passed through the system oil separator.
The dirty, used oil is then stored with the refrigerant in the ISV, and will eventually be charged back to a vehicle in a subsequent recharging process. Recharging refrigerant contaminated with oil into the vehicle reduces air conditioning system performance, and in some instances can result in an electrical short within a compressor of the air conditioning system. What is needed, therefore, is a refrigerant recovery unit that better removes system oil during a recovery operation.